Knuckle swivel for servicing wells

ABSTRACT

A knuckle-swivel ( 10 ) is used with well drilling equipment for protecting helical wound line  62 , which may be wire rope, cable and/or strand, against torsional forces and also providing for angular displacement of sinker bars or other tools during wireline strip over operations to minimize interference with rig equipment ( 80 ) when pulling pipe or tools  64  from a well head.

This is a continuation of application Ser. No. 10/416,190, filed on May9, 2003; as a National Phase Application of International ApplicationNumber PCT/US01/43034, filed on 9 Nov. 2001, claiming priority of U.S.Provisional Application 60/246,756, filed on Nov. 9, 2000; now U.S. Pat.No. 7,217,056, granted on May 15, 2007.

BACKGROUND OF THE INVENTION

Many conventional drilling rigs use a top-drive for pulling pipe and/ortools from a well bore. Powerful motors are used to pull and wind wirerope, cable or strand about a drum located above the derrick floor.Swivels are used in-line with helical wound members such as rope, cableor strand for allowing rotation about a longitudinal axis thereof undertension for minimizing or avoiding straightening of the helical windingsin order to protect the strength and integrity of the rope, cable orstrand by compensating for the torsional force induced by large axialforces on the helical member. Typical forces can be on the order ofseveral tons, or more.

In one typical operation referred to as a “wireline strip overoperation”, a sinker bar is used in-line with the wire rope. Sinker barshave in the past been comprised of a rigid member which may be in theform of a solid bar on the order of 15 to 20 feet in length. Use of sucha sinker bar with a top drive creates interference between the sinkerbar and rig equipment located vertically above the drill pipe;heretofore, it has been necessary to move and relocate the top driveunit out of the way. This is a time consuming operation that is best tobe avoided.

SUMMARY OF THE INVENTION

The invention relates to the use of a unique implement which is nowreferred to as a “knuckle=swivel” and which provides for the multiplefunction of introducing a 360 degree swivel capability for minimizingand/or precluding the above referred torsional forces on the rope, cableor strand and, in addition, provides for a knuckle function to allowangular displacement for minimizing or precluding bending loadstransmitted into the swivel during withdrawal of sinker bars from thewell bore or other tools and the like being pulled around an obstacle.

The present invention is particularly useful for well drillingoperations including but not limited to those utilizing a top drivewinding drum for pulling items from the well bore and, moreparticularly, the invention is intended to be used with “Flexible SinkerBar Assemblies” which are the subject of my U.S. Pat. No. 6,227,292 B1,granted on May 8, 2001; the disclosure of my earlier patent isincorporated herein by reference. An important feature of the presentinvention resides in the combination of the instant knuckle-swivel and asinker bar, either a rigid sinker bar or ideally a flexible sinker bar,in order to minimize or preclude the heretofore requirement of movingthe top drive unit during pulling operations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal, sectional view of a knuckle-swivel inaccordance with the invention.

FIG. 2 is a side elevational view of the knuckle-swivel showing theextent of side rotation.

FIG. 3 is a schematic representation of the knuckle-swivel connected toa helical wound wire rope, cable or strand which comprises part of asinker bar.

FIG. 4 is a schematic view showing a helical wound rope, cable or strandbeing, diverted around rig equipment with the knuckle-swivel located atthe mouth of the well.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A knuckle-swivel body member, generally indicated by the numeral 10,includes a bottom sub 14 having threads 16 at one end thereof andreceiving a bearing pin 18 in its opposite hollow end 20 and beingconnected thereto by a slotted spring pin 22.

An upper sub 24 includes a first threaded end 26 and a second threadedend 28, the latter being connected to the knuckle-swivel body member 10in alignment with bottom sub 14. Body member 10 contains a pair ofbearing cones 30, 30, a pair of bearings cups 32, 32 and a pair ofbearing races 34, 34 which are mounted upon cylindrical posts 36, 36disposed on opposite sides of bearing pin 18. A flat wire compressionspring 40, of a type known as a crest-to-crest spring, is locatedbetween one bearing cup 32 and the adjacent end of upper sub 24 forapplying a constant force against the cup 32 for stabilizing a pluralityof ball bearings 42 between the bearing cones 30, 30 and the bearingraces 34, 34. A grease fitting 44 is provided for passing lubricantthrough a passage 46, it being understood that the lubricant can passthrough spring 40 and protect the various bearing components.

As is best shown in FIG. 1, body member 12 is provided with afrusto-conical surface 50 which limits bearing pin 20 to approximately20 degrees of side-to-side rotation, the extent of rotation being bestshown in FIG. 2. Thus, bearing pin 18 is capable of rotating 360 degreesabout its longitudinal axis within body member 12 in addition to aside-to-side conical movement of 20 degrees.

Referring to FIGS. 3 and 4, it will be seen that the knuckle-swivel 10is secured by a swaged end connector 60 to a line 62, which may be ahelical wound wire rope, or cable, or strand member. It is to beunderstood that helical wound line 62 is protected by knuckle-swivel 10because of the capability of 360 degrees of axial rotation of bearingpin 18 minimizes or precludes torsional forces upon the line 62. In theabsence of such protection, large axial loads would tend to straightenthe helical windings and thereby severely weaken the strength of theline 62. End connector 60 is threaded onto sub 14, and sub 24 can bethreadedly connected to a pipe or tool 64.

It is to be understood that it is conventional in the well drillingindustry to provide a top drive (not shown) in the form of a windingdrum located at or near the top of a derrick or rig, for pulling pipe ortools from the well. It is not unusual for portions of the derrick orrig to be interposed between the well head and the winding drum. As aresult, it has heretofore been necessary to mount the top drive so thatit may be adjustably moved laterally to prevent interference between thepulling line and rig. As is best shown in FIG. 4, line 62, which may bea component of a flexible sinker bar as described in U.S. Pat. No.6,227,292, can be angularly displaced while under load because of theprovision of knuckle-swivel 10. As a result, interference with rigequipment, generally indicated by the numeral 80, is avoided and it isunnecessary to move or relocate the top drive member. Line 62 can betrained over a guide roller (not shown) upwardly of or adjacent the rigequipment 80 for preventing contact during a wireline strip overoperation, or the like.

From the foregoing, the preferred construction of the invention will beobvious to those skilled in this art but it is to be understood thatsome changes in construction and operation are possible withoutdeparting from the spirit and scope of the invention as defined in theclaimed subject matter appended hereto.

1. A knuckle-swivel for use with well servicing equipment comprising:upper and bottom subs, each having threaded portions for connection tosaid well servicing equipment, means for attaching a helical woundpulling line to at least one of said subs, a bearing pin connecting saidupper sub to said bottom sub and having an annular outer surface, a bodymember extending from one of said subs such that one end portion of saidbearing pin is retained within a cavity of said body member and theother end of the bearing pin extends through an opening in the bodymember and connects to the other of said subs, the bearing pin furthercomprising: antifriction bearing means received on and disposed aboutsaid outer surface of said bearing pin for providing relative rotationbetween said upper and bottom subs, said anti-friction bearing meansincluding roller element bearings for accommodating 360 degree rotationof said bearing pin about its longitudinal axis and relative to saidbody member for minimizing torsional forces upon said helical woundpulling line during a pulling operation, and means on said opening forfacilitating angular displacement of said upper sub relative to saidbottom sub.
 2. A knuckle swivel as defined in claim 1 wherein a greasefitting (44) is disposed axially within said one of said subs forproviding lubricant to said bearing member for lubricating said bearingmeans.
 3. A knuckle-swivel as defined in claim 1, wherein a helicalwound pulling line (62) is connected to at least one of said subs viasaid attaching means.
 4. A knuckle swivel as defined in claim 3 whereinsaid line (62) comprises at least a portion of a sinker bar.